The invention relates to novel compositions and a process for making fragrance friendly aluminum zirconium salts that are commonly considered active antiperspirant materials and are covered by FDA OTC Final Monograph as Category I.
The antiperspirant and deodorant market offers a wide diversity of products to meet consumer needs. The physical forms of antiperspirants vary greatly. They include aerosols, pump sprays, squeeze sprays, creams, roll-ons, suspension roll-ons, deodorant sticks, clear gels, soft solids, etc. Different physical forms of final formulations require that antiperspirant actives meet certain specific chemical or physical properties or both to achieve the desired results. Prominently in the hierarchy of consumer wants is long lasting control of fragrance and wetness. Consumers also want their antiperspirant to have excellent sensory properties on application and certain aesthetics.
The reasons for such a variety of individual preference products is that the manufacturers increasingly turn to market segmentation to increase their total share of dollar sales and today's customers have sophisticated expectations. For example, clarity remains a market force in the personal care industry as consumers associate clarity with lack of unsightly white residue on skin and clothing. Given these circumstances, it is evident that growth of individual brands must come primarily through product improvement. This can be achieved either by improving product aesthetics or antiperspirancy, or both. Prospects for such improvements have provided an impetus for the development of newer actives and their modifications to meet specific formulation requirements.
The antiperspirant product group is probably the most demanding in terms of creative (aesthetic) and technical implications when it comes to creating fragrances that are compatible. (Hoffman, H. M. and Ansari, R., Fragrancing of Antiperspirant Products, Reheis Report 11, 1983).
Fragrance is an important part of antiperspirant and deodorant appeal. According to a research(1) (Cult of Personality, Soap, Perfumery & Cosmetics, July 2001, pp. 18–21). Half of all consumers cite fragrance as an important reason for choosing when purchasing antiperspirant devices. Young consumers in particular are influenced by fragrance.
Fragrance plays a key role in personal care products such as deodorants and antiperspirants. It attracts customer interest, inspires the first purchase, retains brand loyalty, communicates sensory perception that the product is doing its job and gives the overall feeling of confidence and personal freshness.
Fragrance is highly important in the development of any new product, while a fragrance may not contribute to the properties of an antiperspirant product, it can by its very nature, influence the consumer's expectations of the product's performance. A successful fragrance must coordinate with the product's attributes. Its initial impact, continuing impression, performance and stability are crucial in ensuring a harmonious commercially attractive product. Thus, good understanding of chemical and physical characteristics of both the fragrance and product and possible interactions are essential to a successful antiperspirant such as a a clear antiperspirant stick that is introduced in the market place. In one situation, for example, dibenzylidene sorbitol as a gelling agent in an antiperspirant found it degraded in the presence of acidic antiperspirant and generated a not too pleasing cherry-almond aroma particularly noticeable on storage due to the release of benzaldehyde. Since then, several attempts have been made to address the issue of the instability of this gelling agent and how it can be stabilized while also retaining the efficacy of incorporated fragrances.
As noted in Nicoll (Nicoll, S., Fragrance Stability in Three Cosmetic Applications, C&T, Vol. 114, No. 7, July 1999, pp. 59–63), when the fragrance is added to the base of a product any of the following reactions may occur:                the product discolors,        off-odors develop in the product,        fragrance is short lived or disappears with time,        fragrance looses its ability to mix with the base either initially or progressively.        
Many reactions can occur when metal ions are present in the product. These metals can develop highly colored oxides when combined with fragrance ingredients leading to product discoloration. Color is one of those issues that can be quite frustrating. Often the color change may not be significant but visual change draws a strong customer response, e.g., if the product does not look good, it cannot be good. Color change can be caused by a number of factors for example citrus and fruit fragrances cause color with antiperspirant active due to oxidation or hydrolysis of esters. Oxidation can be further catalyzed by iron or other materials.
Although antiperspirants and deodorants are two different product groups, they are often grouped together. In fact, the two are quite different in their mode of action and their formulation, requiring different technical considerations. These differences have far reaching implications when it comes to fragrancing these products.
The function of deodorants is essentially to mask underarm odor with fragrance and inhibit the proliferation of bacteria responsible for the sweaty smells. In many cases, a product sold as a deodorant may solely be based on an alcoholic solution of the fragrance and a bactericide. The medium to fragrance is usually mild and the perfumer is able to concentrate largely on the aesthetics in the selection of raw materials for the creation of fragrances. On the other hand, the fragrancing of antiperspirants is very different and hedonically pleasing fragrances for antiperspirants are challenging.
Antiperspirants inhibit eccrine perspiration and thereby reduce wetness; the aluminum salts and aluminum zirconium complexes, the active ingredients of antiperspirants, are also known to have antibacterial activity and must, therefore, inhibit the proliferation of bacteria responsible for the degradation of apocrine sweat, giving rise to malodorous fatty acids and other volatile nitrogeneous compounds. Whatever malodor problem that might remain is supposed to be taken care of by the fragrance. The antiperspirant then becomes a deodorant too and the fragrancing becomes a crucial factor in determining the consumer acceptability of the product.
The majority of antiperspirants use aluminum chlorohydrate or Al/Zr products having Al/Zr ratio from 2:1 to 10:1 and metals to chloride ratio of 0.9:1 to 2.1:1 in micronized dry powder form or solutions depending upon the final product form. All these preparations work under acidic conditions (e.g., a 20% w/w solution of aluminum chlorohydrate has an approximate pH of 4.0), rendering many fragrances unstable in the base. As the metals/anion ratio decreases, the product becomes more efficacious, more acidic and less compatible with fragrances. To compensate for acidity, usually higher amount of glycine is employed which makes the product more expensive. Acidity could also have an effect on its compatibility with fragrance as a source of primary amine, like glycine is likely to react with aldehydes present in fragrance and form imines which impart color to the product. This instability causes changes in odor and induces discoloration of the final formulation over a period of time.
Since a fragrance is a complex mixture of blend of aromatic materials of natural and synthetic origin, it is very difficult to ensure that all the ingredients present will be stable and free from degradative changes induced by the pH of the medium and other changes catalyzed by the metals present. In general, it is recommended that natural oils be avoided, since they invariably contain a great number of chemicals of differing functionalities, making it almost impossible to predict the behavior of the individual components once incorporated into the base. According to Hoffman and Ansari, exception to this is probably the woody complexes based on Patchouly, Cedarwood and Sandalwood. Another point of importance is that aluminum and zirconium salts almost always contain iron as an impurity which complexes with fragrance materials bearing phenolic functionality and causes serious discoloration problems. Stating it differently, the antiperspirant base imposes considerable limitations on the use of fragrance raw materials. It is noted that aldehydic fragrances have dominated this segment of the market; probably the reason is that many aldehydes are fairly stable in the base media. Most of other known types found on the market are only marginally stable.
Although the fragrance industry has provided the formulators of antiperspirants with fragrances that are stable and have consumer acceptance, consumers desire for new fragrances are ever increasing.
Most widely used aluminum zirconium antiperspirants usually contain primary amino acids like glycine as buffers to avoid gelling of aluminum zirconium aqueous system. The source of primary amines present in antiperspirant active can react with aldehydes present in fragrance to form a Schiff base that is usually highly colored. This change in color can be problematic especially because it is usually catalyzed by light or heat exposure.
In summary, it can be stated that antiperspirant bases are acidic, cationic and contain metal ions which can catalyze the degradation of many fragrance ingredients causing odor changes and discoloration. In perfuming, the pH of the antiperspirant product plays an important role. Antiperspirants are typically in the pH range of 3.5 to 4.5 and perfumes are more unstable at lower pH. Many perfume materials react with the aluminum and aluminum zirconium actives used in antiperspirant. This can lead to a change in the odor of the perfume or to a discoloration of the product. Imines are formed when aldehyde reacts with a primary amine to release a water molecule. The glycine, a common component present in aluminum zirconium complexes, is a primary source of amine and can react with fragrances to give a color.
Iron is usually present in USP grade antiperspirant active as an impurity at a fairly high level up to 50 ppm in solution to 125 ppm in powders. Pink coloration of an antiperspirant product is usually traced directly to metal interactions, primarily iron. Other metals such as Mn, Cu, Co, Cr or Ni can cause color generation if they are present in significant amounts.
It has been well established that axillary malodour is caused by biotransformation of non odorous precursors present in apocrine sweat and sebum by the axillary microflora. To counter this, deodorants normally contain bactericides. However, after the initial kill of bacteria, the surviving cells grow, producing a concomitant rise in axillary odor. Long lasting deodorant effect is achievable only if bacterial growth is inhibited for an extended period such as by a controlled release of a bactericide. Another approach is to inhibit bacterial growth by nutrient deprivation, primarily that of iron Fe(III) as has been proposed by L. Andrew and Stephen Makin (Iron Sequestration on Skin: a new route to improved deodorancy, 22nd IFSCC Congress, Edinburgh 2002). The content of that publication and of the patent disclosure in WO 03/007903A, titled “Deodorant Compositions Comprising A Transition Metal Chelator and A Silicon Fluid”, are incorporated herein by reference in their entirety. Based on reported research the indication is that the deprivation of iron Fe(III) has the most profound effect on bacterial growth.
However, it should be recognized that while reduction in iron contribution by antiperspirant is beneficial, it does not deprive microflora of all the iron as there are two other source of iron from the skin, namely losses of iron in sweat and losses of iron in desquamated epithelial cells. The latter are probably fairly constant in the single individual and independent of the amount of sweat lost whereas sweat iron loss vary considerably. Various studies have been reported in the literature concerning the loss of iron and other trace metals through the skin. Concentration of iron values reported in the sweat vary considerably depending upon how the sweat was collected, analytical techniques used and whether the sweat was collected under thermal stress or at room temperature, etc. The following references provide useful insight into trace metal losses through skin. Of particular interest is the iron in cell-free sweat in the underarm area. Brune, M.; Magnusson, B.; Persson, H. and Hallberg, L. reported their findings on the loss of iron in whole body cell-free sweat in eleven healthy men in an article titled Iron Losses in Sweat (Journal of American Clinical Nutrition, Vol. 43, March 1986, pp. 438–443). In this study a new experimental design was used with a very careful cleaning procedure of the skin and repeated consecutive sampling periods of sweat in a sauna. The purpose was to achieve a steady state of sweat iron losses with minimal influence from iron originating from desquamated cells and iron contaminating the skin. Iron loss was directly related to the volume of sweat lost and amounted to 22.5±2.29 μg of iron/liter of sweat. The findings indicated that iron is a physiological constituent of sweat and the iron content of cell rich, compared to cell free, sweat was about five (5) times higher.
Green, et al., (Body Iron Excretion in Man, A Collaborative Study, American Journal of Medicine, Vol. 45, 1968, pp. 336–53) reported sweat iron losses in laundry workers with heavy sweat losses. The calculations of sweat iron losses were based on the rate of decline in specific activity of 55Fe over several years. The average extra iron loss due to the perspiration (from the whole body) calculated from that study was about 0.1 mg/day.
On its web page titled Inspired to Perspire, Gillette Uncovers Sweat Gillette has reported several of the findings about sweat from its experts as follows: (1) the average amount of perspiration from underarms in one hour at room temperature equals 200 mg; (2) the average amount of perspiration from underarms in one hour at room temperature during emotional stress equals 700 mg; (3) underarms are the top sweat producing areas of the body; (4) men have a much higher sweat rate than women; (5) the usage rate of antiperspirant and deodorant varies with the age group; (6) men use an antiperspirant or deodorant an average of 7.9 times a week and women 8.3 times a week; (7) young men and women use antiperspirants and deodorants more frequently than any other group; (for example, women age 13–17 use 10.3 times/week and men age 15–17 use 9.8 times/week); and (8) more than 90% of men and women use a deodorant or an antiperspirant. Thus, it is safe to assume that on an average antiperspirant is used at least once/day.
Using the information of iron concentration in cell free sweat as determined by Brune et al., and the average amount of perspiration from underarms reported by Gillette, iron contribution by cell free sweat in underarm areas is computed to be 0.108 μg /day.
Maximum iron content of a typical USP grade antiperspirant powder can be 125 ppm and average usage rate of an antiperspirant product per application per underarm is about 0.4±0.05 gm. According to the final OTC monograph issued by FDA in June 2003, maximum anhydrous solids content of aluminum zirconium active in an antiperspirant formulation can be 20%. Thus, the maximum iron contribution by Al/Zr antiperspirant salt to underarm can be about 28.8 μg/day. Assuming an iron content of 70 ppm in Al/Zr active iron contribution could be about 16 μg/day.
While the exact amount of iron contribution by sweat and desquamation in the underarms area is not known the aforementioned computed numbers give some perspective as to the amount of iron involved and whether reduction in iron content of the active would help improve deodorancy of antiperspirant product or not. It is not known whether the iron from the active is readily available to the microflora as it is from the iron carrier protein transferring, present in eccrine sweat. Since the iron contribution by antiperspirant appears to be significant, reduction in its value is hypothesized to improve deodorancy of the final product assuming that iron from the active is available as a nutrient to the axillary microflora.
Thus, the objective is to make aluminum zirconium actives with low trace metal impurities, low iron, glycine free and at least equal in efficacy to the products currently used.
Accordingly, to improve fragrance compatibility it is preferred to have an aluminum zirconium active without primary amine, with low or no iron content and very low Mn, Co, Cr, Cu and Ni levels.
Because the antiperspirant market is flooded with a variety of products and this imposes many different requirements on antiperspirant actives and finished formulations and because almost all forms of antiperspirant formulations are scented compatibility of different actives in different product forms with fragrances is extremely important and the nemesis of all product marketers is color change.
With reference to the prior art patents, aluminum zirconium antiperspirant salts have been known since about 1954; numerous patents have been issued for the processes and compositions of making these salts. Patent documents which are cited in connection with the disclosed invention are U.S. Pat. No. 2,814,585 (Daley), U.S. Pat. No. 2,854,382 (Grad), GB 1,353,916 (Bolich), GB 2,075,289 (Mackles), U.S. Pat. No. 3,979,510 (Rubino), U.S. Pat. No. 4,017,599 (Rubino), U.S. Pat. No. 4,331,609 (Orr), U.S. Pat. No. 4,775,528 (Callaghan), U.S. Pat. No. 4,871,525 (Giovenniello), U.S. Pat. No. 4,900,534 (Inward), U.S. Pat. No. 5,225,187 (Carmody), U.S. Pat. No. 5,296,623 (Katsoulis), U.S. Pat. No. 5,33,751 (Curtin), U.S. Pat. No. 5,718,876 (Parekh), U.S. Pat. No. 6,066,314 (Tang), U.S. Pat. No. 6,375,937 (Chopra), U.S. Pat. No. 6,436,381 (Carrillo), etc.
Some of these aluminum zirconium antiperspirant salts are described as having enhanced efficacy, which means that they provide greater sweat reduction than conventional antiperspirant salts. The enhanced efficacy salts are typically differentiated from conventional antiperspirant salts by reference to the various aluminum peaks that can be identified when the salt is analyzed by size exclusion chromatography, typically HPLC. For more discussion on peak assignments of HPLC chromatography reference is made to copending application Ser. No. 10/807,996 filed Mar. 24, 2004.
A common aspect of all the patents cited is that they use mostly neutral amino acid or salts of amino acid to avoid gelling and to reduce acidity when basic aluminum halides and zirconium salts, like zirconium oxychloride (ZrOCl2) or zirconium hydroxychloride (ZrO(OH)Cl) solutions, are combined to create more efficacious aluminum zirconium antiperspirants. In some of the recent patents, for example, U.S. Pat. No. 6,066,314 discloses post addition of glycine to aluminum zirconium salts containing glycine in an amount of 1:1.2–1.5 of zirconium to amino acid on a weight weight basis. Marginal, if any, associated increase in efficacy is expected. However, the product is more expensive. Also, U.S. Pat. No. 6,375,937 comprises aluminum zirconium salts which have a metal to chloride molar ratio in the range of 0.9–1.2:1 and glycine:zirconium molar ratio greater than 1.3:1 and more particularly greater than 1.4:1. Such excessive amounts of glycine increases cost of the product significantly and probably make the product less compatible with fragrances. In U.S. Pat. No. 2,814,585 Daley discloses (column 3, lines 50 to 70) that high concentration of the amino acids in aluminum zirconium antiperspirant compositions have a deleterious effect upon the efficacy of the composition. Moreover, antiperspirant preparations containing such large amount of amino acids are not economically attractive from a marketing standpoint.
Accordingly an object of the invention is to develop a process for making aluminum zirconium antiperspirant salt over the entire range covered by the OTC Monograph without the requirement of inclusion of any amino acid or salts of amino acids or other buffers.
U.S. Pat. Nos. 4,775,528; 5,114,705; 5,225,187; 5,486,347; 5,589,196; 5,955,064; 5,939,057; 6,066,314; 6,074,632; 6,451,296 B1; and EP 0633203 A1, and WO 01/56539 disclose aluminum zirconium antiperspirant compositions containing either both glycine and polyhydric alcohol or only polyhyric alcohol. With respect to formulations containing solely polyhydric alcohol the prior art indicates that stable and efficacious antiperspirant is obtained by eliminating glycine and replacing it with polyhydric alcohol. While the replacement of glycine by polyhydric alcohol in aluminum zirconium yields efficacious antiperspirant, it also tends to introduce an undesirable tackiness to the antiperspirant active and formulations of this kind have limited product application.
Thus, it is highly desirable to have a stable and effective aluminum zirconium active which is free of glycine as well as polyhydric alcohol.
In U.S. Pat. No. 2,906,668, Beekman disclosed a process for preparing aluminum/zirconium complex with aluminum to zirconium atomic ratio in the range of 2 to 10; but in both the examples cited, a gel was formed which was changed to opalescent or cloudy liquid by heating. Gelling is due to polymerization of zirconium species and this renders the product to be less efficacious. Daley, in U.S. Pat. No. 2,814,585 discloses that prevention of gelling of antiperspirant preparation is extremely important since gels have been found to have limited antiperspirant properties so as to be considered useless from a practical standpoint.
In U.S. Pat. No. 3,405,153 Jones disclosed a process for preparing aluminum-zirconium complex by adding zirconium oxychoride to hot aluminum chlorohydroxide and the gel that was formed was said to be essentially dissolved with prolonged heat and agitation and reflux which yielded cloudy solution. Thus it suffers from the same limitations as those for U.S. Pat. No. 2,906,668 noted above.
In U.S. patent application Ser. No. 10/625,038 is disclosed a process to make aluminum zirconium salts without amino acid and polyhydric alcohol, but the process is not capable of producing all the aluminum zirconium salts approved by FDA under the OTC Final Monograph issued on June 2003. This is demonstrated on the FIGURE of the accompanying drawing. Only products covered by the shaded area in FIG. 1 can be made using the system described in that patent application. Specific products that can be prepared using the process of the above mentioned patent application include aluminum zirconium tetrachlorohydrate with Al/Zr atomic ratio from about 2 to 6 and metal/chloride atomic ratio from about 0.9 to 1.25; aluminum/zirconium octachlorohydrate having Al/Zr atomic ratio from about 6 to about 10 and metal to chloride atomic ratio about 0.9 to about 1.5 and aluminum zirconium pentachlorohydrate having Al/Zr atomic ratio from about 6 to 10 and metal to chloride atomic ratio of about 1.51 to about 1.65. According to the novel process of the present invention, it has been discovered that all of the aluminum zirconium products under FDA OTC Final Monograph issued on June 2003, i.e., those encompassed by the FIGURE of the drawing can be made. It is important to note that the two most widely used aluminum zirconium antiperspirant are aluminum zirconium trichlorohydrex (with Al/Zr ratio of 3 to 6 and M/Cl ratio of 1.51 to 2) and aluminum zirconium tetrachlorohydrex (with Al/Zr ratio in the range of 3–5 and metals to chloride ratio of 1.35 to 1.5) and with respect thereto, process of U.S. patent application Ser. No. 10/625,038 has very limited application. Also, that application does not address the issue of color formation (fragrance compatibility) achieved by the novel product of the present invention in which iron and trace metal (Co, Cr, Ni, Mn and Cu) levels are closely controlled to minimize color formation with the fragrances. Fragrances are more stable and compatible with higher metals to chloride ratio aluminum zirconium products, but such products are incapable of being made with the process of U.S. patent application Ser. No. 10/625,038 as shown by FIG. 1. In summary, the novel process of the present invention is unique in that it facilities formulation of the entire range of very low iron aluminum zirconium antiperspirant salts that fall within the scope of the OTC Final Monograph without incorporating amino acid or polyhydric alcohol; which are cost effective; which minimize the probability of the final product's color change; which are more compatible with fragrance; and which improve deodorancy by reducing iron contribution to underarm area.
U.S. Patent Application Publication No. 2003/0138389 A1 discloses a deodorant antiperspirant comprising an aluminum chlorohydrate with an iron content of less than 20 ppm on a dry basis having improved efficacy and deodorancy for low iron product (10 ppm) compared to high iron product (80 ppm). The disclosure of that patent application is incorporated herein in its entirety by the reference. No disclosure is contained in that application which deals with color formation or fragrance compatibility for low iron glycine free aluminum zirconium product or regarding the preparation of more cost effective amino acid free aluminum zirconium products.
U.S. Pat. No. 6,451,296 B1 discloses that low molecular weight aluminum species as measured by HPLC Band IV (or peak 5) lead to more efficacious products. However, it is important to note that U.S. Pat. No. 6,451,296 B1 teaches use of high concentration of polyhydric alcohol during the reaction phase to avoid polymerization of zirconium species and does not teach how to make low iron low trace metal, glycine free and cost effective aluminum zirconium salts which are more compatible with fragrances. Also the product of this patent tend to be tacky and have limited application. In Carrillo, et al., U.S. Pat. No. 6,436,381 improved efficacy is correlated with low metal to chloride (0.9:1 to 1:1) aluminum zirconium products with peak 5 (or Band IV). The disclosure of U.S. Pat. No. 6,436,381 does not embrace glycine free aluminum zirconium salts over the metal/chloride ratio range greater than 1.1. The requisite process parameters and composition of the present invention are outside those employed in the patent.
None of the foregoing referenced prior art discloses or teaches the process of the present invention: of making low iron (less than 30 ppm, preferably less than 20 ppm, more preferably less than 10 ppm and most preferably less than 5 ppm) aluminum zirconium antiperspirant salts without amino acid or amino acid salt or polyhydric alcohol; having very low trace metal (Co, Cr, Ni, Mn, and Cu) impurity level (less than 2 ppm and more preferably less than 1 ppm) and which are fragrance friendly, very cost effective and very efficacious. Because zirconium and amino acids or salts of amino acids are the most expensive ingredients in any aluminum zirconium antiperspirant actives, the elimination of glycine and/or its salts and increasing the Al/Zr ratio from 3.5–4 to 7–8 without sacrificing efficacy makes the novel product of this invention most cost effective and attractive from marketing standpoint. Where efficacy comparable to that of enhanced efficacy salt is desired, it can be achieved by lowering the concentration of basic aluminum chloride to about 15–20 wt % and lowering Al/Zr ratio from 7–8 to 3–4 range. Addition of highly acidic ZrOCl2 or ZrO(OH)Cl result in depolymerization of aluminum species resulting in higher concentration of aluminum species in peaks II, IIII and IV.